On 4/3/24 02:35, Teus Benschop wrote:
A snmpd was set to listen on 10 ports through multiple entries like
“agentaddress tcp:<port>” in the snmpd.conf file.
It was verified through snmpget that the snmpd listens on all 10 ports.
Function “netsnmp_callback_open” in file
snmplib/transports/snmpCallbackDomain.c was patched to write a few
debug messages.
It appears that the function “netsnmp_callback_open” is called once.
It sets the “callback_ss->local_port” to “((netsnmp_callback_info *)
callback_tr->data)->callback_num”, which is 1.
In the handler callback function, the
reqinfo->asp->session->local_port is 0 while processing each snmpget.
You wrote "Make sure that session->local_port is set correctly." I
studied the code to set this properly, but didn't manage to get the
port number set correctly.
I think this is the callchain for registering the ports that the agent
listens on:
init_master_agent()
netsnmp_agent_listen_on()
netsnmp_transport_open_server()
netsnmp_register_agent_nsap()
netsnmp_sess_config_transport()
snmp_add()
snmp_sess_add_ex()
transport->f_setup_session()
One possible approach is to implement the .f_setup_session() callback in
the TCP transport and to make it copy the port information from the
transport into the session.
Best regards,
Bart.
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